Bio-based polyester polyol for hot melt adhesive as well as preparation method and application of bio-based polyester polyol

Abstract

The invention relates to the field of hot melt adhesives, and particularly discloses bio-based polyester polyol for a hot melt adhesive as well as a preparation method and application of the bio-based polyester polyol. The bio-based polyester polyol for the hot melt adhesive is dimer acid polyester polyol containing an epoxy phosphate group; the preparation method comprises the following steps: performing hydrolytic acidification on flax oil to obtain unsaturated fatty acid; synthesizing a double-bond-containing dimer acid intermediate by a low-temperature enzyme catalysis method; introducing an epoxy group through double-bond epoxidation reaction; carrying out functionalization reaction with a phosphoric acid group to construct epoxy phosphate functionalized dimer acid; and constructing a rigid double-ring skeleton structure to prepare the bio-based polyester polyol. The bio-based polyester polyol disclosed by the invention can be used for preparing a hot melt adhesive, and the hot melt adhesive has relatively high bio-based content, bonding strength, base material universality and initial adhesion to a polar base material.

Description

Technical Field

[0001] This application relates to the field of hot melt adhesives, and more specifically, to a bio-based polyester polyol for hot melt adhesives, its preparation method, and its application. Background Technology

[0002] Reactive polyurethane hot melt adhesive (PUR) is a high-performance, environmentally friendly adhesive that contains no water or solvents and has a solid content of 100%. In recent years, it has been widely used both domestically and internationally and has been successfully applied in building materials, furniture and woodworking, electronics and electrical appliances, automobile manufacturing, bookbinding, shoemaking and textile processing and other fields.

[0003] Despite their wide market applications, existing reactive polyurethane hot melt adhesives often use petroleum-based polyester polyols as raw materials, resulting in hot melt adhesives with significant technical defects: 1. Low bio-based content: The bio-based content of commonly available reactive polyurethane hot melt adhesives on the market is generally less than 20%, which makes it difficult to meet the increasingly stringent requirements of environmental regulations such as EU REACH.

[0004] 2. Insufficient bonding strength to metal substrates: Existing reactive polyurethane hot melt adhesives typically use petroleum-based polyester polyols as raw materials. Moisture present at the metal interface can penetrate into the adhesive layer, causing hydrolysis of polyester segments and resulting in a significant decrease in bonding strength over time. Petroleum-based polyester polyols also generally suffer from insufficient polarity, making it difficult to form sufficiently strong hydrogen bonds or chemical bonds on the metal surface. This results in low bonding strength of the product to metal substrates, severely limiting its widespread use in metal bonding applications.

[0005] 3. Poor substrate compatibility: When used in woodworking, furniture, automotive and other fields, existing reactive polyurethane hot melt adhesives often have poor adaptability to different substrates, and manufacturers need to develop specific product models for different substrates.

[0006] 4. Low initial tack to polar substrates: Many existing products have insufficient initial tack to certain difficult-to-bond polar substrates such as PA, ABS and other modified plastics, which affects operating efficiency. Summary of the Invention

[0007] To overcome the deficiencies of the prior art and improve the bio-based content, bonding strength, substrate versatility, and initial tack to polar substrates of hot melt adhesives, this application provides a bio-based polyester polyol for hot melt adhesives, its preparation method, and its application.

[0008] In a first aspect, this application provides a bio-based polyester polyol for hot melt adhesives, employing the following technical solution: A bio-based polyester polyol for hot melt adhesives, wherein the bio-based polyester polyol is a dimeric acid polyester polyol containing epoxy phosphate groups.

[0009] By adopting the above technical solution, the hot melt adhesive prepared from this bio-based polyester polyol has high bio-based content, high bonding strength, broad substrate compatibility, and high initial tack to polar substrates.

[0010] Secondly, this application provides a method for preparing a bio-based polyester polyol for hot melt adhesives, using the following technical solution: A method for preparing a bio-based polyester polyol for hot melt adhesives includes the following steps: (1) Flaxseed oil is put into a reaction vessel, and NaOH aqueous solution and water are added under N2 protection to hydrolyze it. Then H2SO4 aqueous solution is added for acidification. After centrifugation, washing and distillation are performed to obtain unsaturated fatty acids. (2) Under N2 protection, antioxidants and unsaturated fatty acids were added to the reactor, the temperature was raised, lipase was added, and a chain terminator was added after the reaction to obtain unsaturated dimers; (3) Under N2 protection, the unsaturated dimer was vacuum dehydrated and dried, cooled to 50°C, antioxidant and chelating agent were added, stirred evenly, hydrogen peroxide was added dropwise for oxidation, and after the reaction, the aqueous phase was washed until it was neutral, the organic layer was separated, and vacuum dehydrated to obtain epoxidized dimer acid. (4) Under N2 protection, add epoxidized dimer acid to the reactor, heat up, add diluted phosphoric acid catalyst dropwise, after reaction, cool down to below 0-5℃, add pyridine catalyst, continue reaction, wash until the aqueous phase is neutral, separate the organic phase, dehydrate under vacuum to obtain bio-based epoxidized phosphorylated dimer acid monomer. (5) Add a mixture of bio-based epoxy phosphorylated dimer monomers and one or more of isosorbide, bio-based diacid and bio-based diol to the reactor in proportion, purge with nitrogen to replace air, and carry out esterification reaction by heating until the acid value drops to 15-22 mgKOH / g. Gradually evacuate the system to reduce the pressure to ≤-0.1 kPa, remove residual water and small molecule byproducts until the acid value is ≤2 mgKOH / g and the hydroxyl value reaches the target value. After the reaction is completed, cool to room temperature, filter to remove impurities, and obtain dimer polyester polyol containing epoxy phosphoric acid groups.

[0011] By employing the above-mentioned technical solution, a low-temperature enzymatic catalysis method is used to synthesize a dimer acid intermediate containing double bonds. This process can efficiently retain double bonds, with a retention rate >90%, providing a foundation for subsequent efficient epoxidation. Furthermore, the aforementioned dimer acid containing double bonds undergoes a highly selective double-bond epoxidation reaction, achieving selective introduction of epoxy groups. The double-bond epoxy rate is >70%, significantly increasing the crosslinking density after curing. This is crucial for the final preparation of the hot melt adhesive and achieving its high final strength and excellent universal adhesion to various substrates (wood, plastic, metal). The obtained epoxy groups are further functionalized with phosphate groups, successfully introducing the desired epoxy phosphate ester groups onto the dimer acid molecule, constructing the key epoxy phosphate ester-functionalized dimer acid. After preparing the hot melt adhesive, the phosphate groups can form strong and stable chemical bonds, such as phosphate bonds, with metal surface oxides / metal ions, significantly enhancing the initial adhesion and bonding strength of the adhesive on the metal substrate. Polyester polyols possess excellent structural design. Based on the rigid six-membered ring structure of the aforementioned epoxy phosphate-functionalized dimer acid and the rigid bicyclic backbone provided by isosorbide, a polyester polyol with a specific rigid bicyclic backbone structure was designed and synthesized. The high crosslinking density of the epoxy groups and the strong metallic bonding force of the phosphate groups produce a significant synergistic effect, enabling the hot melt adhesive prepared from this bio-based polyester polyol to achieve ultra-high shear strength at the metal interface after curing. The hot melt adhesive prepared from this bio-based polyester polyol exhibits high bio-based content, high adhesive strength, broad substrate compatibility, and good initial tack to polar substrates.

[0012] Optionally, the hydrogen peroxide has an epoxy rate of 70% to 80% and an epoxy value of 0.25 mol / 100g to 0.28 mol / 100g.

[0013] Optionally, in step (3), the molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.2:1 to 1.3:1.

[0014] By adopting the above technical solution, too little hydrogen peroxide will result in a low epoxy rate, while too much hydrogen peroxide will cause side reactions, causing the epoxy value to decrease instead of increase.

[0015] Optionally, in step (4), the reaction rate of the epoxide groups of the phosphoric acid with the epoxidized dimer acid is 15%.

[0016] Optionally, in step (5), the weight of the bio-based epoxy phosphorylated dimer monomer is 31.2% to 81% of the total weight of all raw materials; the weight of the isosorbide is 12.2% to 29.8% of the total weight of all raw materials; the weight of the bio-based diacid is 0% to 28.7% of the total weight of all raw materials; and the weight of the bio-based diol is 0% to 10.3% of the total weight of all raw materials.

[0017] The hydroxyl value of bio-based polyester polyols used in hot melt adhesives can be controlled between 15 and 55 mg KOH / g. For preparing hot melt adhesives with higher performance, bio-based polyester polyols with a hydroxyl value (OH count) of 35–45 mg KOH / g are preferred. The hydroxyl value is defined as the number of milligrams of potassium hydroxide required to neutralize the acetylation of one gram of a substance containing free hydroxyl groups and absorb the absorbed acetic acid. The hydroxyl value can be determined, for example, by titration.

[0018] The raw materials for the bio-based polyester polyols used in hot melt adhesives are preferably derived from renewable resources. The bio-based diacids are preferably selected from succinic acid, azelaic acid, sebacic acid, furanyl dicarboxylic acid, dimerized fatty acids, and mixtures of several of these in any proportion. The bio-based diols are preferably diols having 2 to 8, preferably 3 to 6 carbon atoms, particularly iso-1,2-propanediol, 1,3-propanediol, 1,4-butanediol, isosorbide, or mixtures of several of these.

[0019] Thirdly, this application provides an application of bio-based polyester polyols for hot melt adhesives, employing the following technical solution: Application of a bio-based polyester polyol for hot melt adhesives, wherein the bio-based polyester polyol can be used to prepare hot melt adhesives comprising an isocyanate compound and at least one bio-based polyester polyol.

[0020] The hot melt adhesive prepared by adopting the above technical solution has high bio-based content, high bonding strength, broad substrate compatibility, and high initial tack to polar substrates.

[0021] The NCO content needs to be controlled; too little will result in insufficient strength, while too much will easily generate bubbles during curing, affecting the application of hot melt adhesive.

[0022] Optionally, the hot melt adhesive contains 35% to 65% by weight of bio-based polyester polyols.

[0023] We were surprised to find that keeping the amount of the epoxy phosphate-based dimer polyester polyol portion within the required range ensured that the hot melt adhesive exhibited high initial strength and high shear strength.

[0024] Optionally, the coating temperature of the hot melt adhesive is 110–150°C.

[0025] Optionally, the hot melt adhesive has a viscosity of 1000–100000 mPa·s, measured at 120°C. The viscosity is measured according to ISO 2555:2018.

[0026] The isocyanate compound is preferably selected from 1,5-naphthylene diisocyanate (NDI), 2,4'- or 4,4'-diphenylmethylene diisocyanate (MDI), isomers of methyl phenylene diisocyanate (TDI), triphenylmethylene triisocyanate (MIT), hydrated diphenylmethylene triisocyanate (H12MDI), tetramethylene xylene diisocyanate (TMXDI), isoflurone diisocyanate (IPDI), phenyl dimethyl diisocyanate (XDI), hexane-1,6-diisocyanate (HDI), pentamethylene diisocyanate (PDI), dicyclohexylmethane diisocyanate, and mixtures thereof. Preferably, one isocyanate compound is diphenylmethylene diisocyanate (4,4'-MDI) (NCO content 33.6%).

[0027] In summary, this application has the following beneficial effects: Because this application employs a low-temperature enzyme-catalyzed high-efficiency synthesis process, highly selective epoxidation technology, the introduction of functional phosphate ester groups, and a unique bicyclic molecular skeleton design, it has prepared a bio-based polyester polyol for hot melt adhesives. The hot melt adhesive prepared with this polyol can effectively avoid the problems of polyester segment hydrolysis degradation and strength reduction that may occur during long-term use, and has high bio-based content, bonding strength, substrate universality, and initial adhesion to polar substrates. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments shall be performed under conventional conditions or conditions recommended by the manufacturer, and the raw materials used in the following embodiments shall be commercially available unless otherwise specified.

[0029] Flaxseed oil was purchased from Guangzhou Panyu Zhongxin Oil & Chemical Co., Ltd.

[0030] The hydrogen peroxide was purchased from Shandong Zhangqiu Mingyue Chemical Co., Ltd.

[0031] Ethanol, phosphoric acid, and 4-dimethylaminopyridine were purchased from Tianjin Yongda Chemical Reagent Co., Ltd.

[0032] Isosorbide was purchased from Jinan Hongbaifeng Industry and Trade Co., Ltd.

[0033] Sebacic acid was purchased from Hengshui Jinghua Chemical Co., Ltd.

[0034] 1,2-Propanediol was purchased from Zhongke Baiyijin Zhengzhou New Energy Co., Ltd.

[0035] 1,4-Butanediol was purchased from Beijing Green Kangcheng Biotechnology Co., Ltd.

[0036] Diphenylmethylene diisocyanate (4,4'MDI), purchased from Wanhua Chemical Group Co., Ltd., WANNATE® MDI-100.

[0037] Example:

[0038] Example 1

[0039] A bio-based polyester polyol for hot melt adhesives, wherein the bio-based polyester polyol is a dimeric acid polyester polyol containing epoxy phosphate groups.

[0040] A method for preparing bio-based polyester polyols for hot melt adhesives includes the following steps: (1) Add 500g of linseed oil to the reaction vessel, heat to 65℃, slowly add 200g of 25% NaOH aqueous solution and 200g of deionized water under N2 protection, control the temperature at 70℃ during the addition, heat to 80℃ after the addition is complete, keep the temperature for 5 hours, then cool down to 65℃, finally add 400g of 15% H2SO4 aqueous solution, stir for 1 hour, then centrifuge, wash 3 times with 55℃ warm water until the washing water is neutral, and finally dehydrate and distill for 2 hours at 95℃ and vacuum degree -0.095MPa to obtain unsaturated fatty acids.

[0041] (2) Under N2 protection, add 5g of antioxidant, namely ST606 of Senior (Shandong) New Material Technology Co., Ltd., and 1kg of unsaturated fatty acid to the reactor, heat to 60℃, add 100g of lipase (Novozymes, Novozym®435), react for 7 hours, and then add 200g of chain terminator ethanol to obtain unsaturated dimer.

[0042] (3) Under N2 protection, 1 kg of unsaturated dimer was added to the reactor and dehydrated and dried at 80°C and -0.095 MPa vacuum for 1 hour. The temperature was then lowered to 50°C, and 3 g of antioxidant (ST606 from Sinier (Shandong) New Material Technology Co., Ltd.) and 1 g of chelating agent (Lanxess, Baypure® CX100) were added. After stirring evenly, 300 g of hydrogen peroxide was slowly added dropwise at a reaction temperature controlled at 60°C. After the addition was complete, the reaction was continued at 60°C for 5 hours. After the reaction was completed, the mixture was transferred to a separatory funnel and washed three times with warm water at 65°C until the aqueous phase was neutral. The organic layer was separated and dehydrated at 80°C and -0.095 MPa vacuum to obtain a light yellow epoxidized dimer acid. The epoxy rate of the hydrogen peroxide was 72%, and the epoxy value was 0.25 mol / 100 g. The molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.25:1.

[0043] (4) Under N2 protection, 1 kg of epoxidized dimer acid was added to the reactor, the temperature was raised to 45°C, and 11 g of diluted phosphoric acid solution (85% aqueous solution) was slowly added dropwise over 2 hours. The reaction temperature was controlled at 45°C. After the addition was completed, the reaction was continued at this temperature for 2 hours. The temperature was then lowered to below 0-5°C, pyridine catalyst was added, and the reaction was continued for 5 hours. After the reaction was completed, the reaction mixture was washed 4 times with warm water at 55°C until the aqueous phase was neutral. The organic phase was separated and dehydrated for 3 hours at 80°C under high vacuum (<-0.095 MPa) to obtain the bio-based epoxidized phosphorylated dimer acid monomer. The reaction rate of phosphoric acid with the epoxy group of the epoxidized dimer acid was 15%.

[0044] (5) A mixture of bio-based epoxy phosphorylated dimer monomer and one or more of isosorbide, bio-based diacid, and bio-based diol is added to the reactor in a certain proportion. In this embodiment, 666g of bio-based epoxy phosphorylated dimer monomer, 204g of isosorbide, 222g of sebacic acid (selected as bio-based diacid), and 76g of 1,2-propanediol (selected as bio-based diol) are used. Nitrogen gas is introduced to replace the air. The esterification reaction is carried out by heating: slowly heating to 145℃, water begins to be discharged, and the top temperature of the fractionation column is controlled to be ≤100℃ (to prevent the polyol from volatilizing). The temperature is gradually increased to 230℃ until more than 90% of the theoretical water output is obtained, that is, the acid value drops to 15-22mgKOH / g. After esterification, the system pressure is gradually reduced to ≤-0.1 kPa by gradually evacuating the vacuum (first low vacuum and then high vacuum) to remove residual water and small molecule byproducts until the acid value is ≤2 mgKOH / g and the hydroxyl value reaches the target value. After the reaction is completed, the system is cooled to room temperature and filtered to remove impurities, thus obtaining a dimer acid polyester polyol containing epoxy phosphate groups.

[0045] Application of bio-based polyester polyols in hot melt adhesives: Bio-based polyester polyols can be used to prepare hot melt adhesives, which contain isocyanate compounds and at least one bio-based polyester polyol. The isocyanate compound selected is diphenylmethylene diisocyanate (4,4'-MDI) (NCO content 33.6%).

[0046] The preparation method of hot melt adhesive includes the following steps: (1) Preparation of bio-based crystalline polyester polyol: Dicarboxylic acid (sebacic acid) and polyol (1,4-butanediol) were added to the reactor at a molar ratio of 1:1.2, and nitrogen gas was introduced to replace the air. The mixture was slowly heated to 145°C, and water began to be discharged. The top temperature of the fractionation column was controlled to be ≤100°C (to prevent the polyol from volatilizing). The temperature was gradually increased to 230°C until more than 90% of the theoretical water output was obtained (the acid value was reduced to 15-22 mgKOH / g). After esterification, the system pressure was gradually reduced to ≤-0.1 kPa (low vacuum first, then high vacuum) to remove residual water and small molecule byproducts until the acid value was ≤2 mgKOH / g and the hydroxyl value reached 30 mgKOH / g. After the reaction was completed, the mixture was cooled to room temperature and filtered to remove impurities, thus obtaining the bio-based crystalline polyester polyol.

[0047] (2) Add 52 kg of bio-based crystalline polyester polyol, 37.5 kg of bio-based polyester polyol for hot melt adhesive in this embodiment, and 0.2 kg of antioxidant (RIANOX®1010, Tianjin Lianlong New Material Co., Ltd.) to the reactor and dehydrate under vacuum at 120°C to -0.95 MPa for 2 hours. This step is used to remove water and prevent side reactions between water and isocyanate from affecting the strength of the hot melt adhesive.

[0048] (3) After cooling to 100℃, add 10.3kg of isocyanate and heat to 115±5℃.

[0049] (4) After reacting for 4 hours, a reasonable NCO value is obtained, i.e., the NCO content is 1.2%, and a hot melt adhesive is obtained. The solid content of the hot melt adhesive is 100%, and the coating temperature can be 110-150℃.

[0050] Example 2 The difference between this embodiment and Embodiment 1 is that: In preparing the bio-based polyester polyol for hot melt adhesive, the epoxy rate of hydrogen peroxide in (3) of this embodiment is 72%, and the epoxy value is 0.26 mol / 100g. The molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.2:1. In (5), the raw materials and amounts are different. In this embodiment, 350g of bio-based epoxy phosphorylated dimer monomer, 334g of isosorbide, 322g of sebacic acid is selected as the bio-based diacid, and 116g of 1,4-butanediol is selected as the bio-based diol.

[0051] The difference between the hot melt adhesive prepared using bio-based polyester polyols in this embodiment and that in Example 1 is as follows: The raw material usage for the hot melt adhesive is as follows: 45.9 kg of bio-based crystalline polyester polyol, 43.5 kg of bio-based polyester polyol for hot melt adhesive in this embodiment, 0.1 kg of antioxidant (Tianjin Lianlong New Material Co., Ltd., RIANOX®1010), and 10.5 kg of isocyanate.

[0052] Example 3 The difference between this embodiment and Embodiment 1 is that: In preparing the bio-based polyester polyol for hot melt adhesive, the epoxy rate of hydrogen peroxide in (3) of this embodiment is 80%, and the epoxy value is 0.28 mol / 100g. The molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.3:1. The raw materials and amounts in (5) are different. In this embodiment, 666g of bio-based epoxy phosphorylated dimer monomer, 100g of isosorbide, no bio-based diacid, and 56g of 1,4-butanediol are used as the bio-based diol.

[0053] The difference between the hot melt adhesive prepared using bio-based polyester polyols in this embodiment and that in Example 1 is as follows: The raw material amounts for the hot melt adhesive are: 42.8 kg of bio-based crystalline polyester polyol, 46 kg of bio-based polyester polyol for hot melt adhesive in this embodiment, 0.2 kg of antioxidant (Tianjin Lianlong New Material Co., Ltd., RIANOX®1010), and 11 kg of isocyanate.

[0054] Example 4 The difference between this embodiment and Embodiment 1 is that: In preparing bio-based polyester polyols for hot melt adhesives, the epoxy rate of hydrogen peroxide in (3) of this embodiment is 75%, and the epoxy value is 0.27 mol / 100g. The molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.25:1. The raw materials and amounts in (5) are different. In this embodiment, there is 666g of bio-based epoxy phosphorylated dimer monomer, 204g of isosorbide, no bio-based diacid, and no bio-based diol.

[0055] The difference between the hot melt adhesive prepared using bio-based polyester polyols in this embodiment and that in Example 1 is as follows: The raw material amounts for the hot melt adhesive are: 28.5 kg of bio-based crystalline polyester polyol, 61 kg of bio-based polyester polyol for hot melt adhesive in this embodiment, 0.2 kg of antioxidant (Tianjin Lianlong New Material Co., Ltd., RIANOX®1010), and 10.3 kg of isocyanate.

[0056] Example 5 The difference between this embodiment and Embodiment 1 is that: In preparing the bio-based polyester polyol for hot melt adhesive, the epoxy rate of hydrogen peroxide in (3) of this embodiment is 74%, and the epoxy value is 0.27 mol / 100g. The molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.25:1. The raw materials and amounts in (5) are different. In this embodiment, 666g of bio-based epoxy phosphorylated dimer monomer, 164g of isosorbide, no bio-based diacid, and 55g of 1,2-propanediol are used as the bio-based diol.

[0057] The difference between the hot melt adhesive prepared using bio-based polyester polyols in this embodiment and that in Example 1 is as follows: The raw material usage for the hot melt adhesive is as follows: 43 kg of bio-based crystalline polyester polyol, 46 kg of bio-based polyester polyol for hot melt adhesive in this embodiment, 0.3 kg of antioxidant (Tianjin Lianlong New Material Co., Ltd., RIANOX®1010), and 10.7 kg of isocyanate.

[0058] Comparative example:

[0059] Comparative Example 1

[0060] Purchased from the market, the polyester polyol brand and model is STEPANPOL®PN-110 from the USA, which is a phthalic acid-based polyester polyol.

[0061] The preparation method of hot melt adhesive is as follows: (1) Based on a total mass of 100 kg of all raw materials for hot melt adhesive, add 23% of the total mass of crystalline polyester polyol (Dynacoll 7360); 46% of the total mass of STEPANPOL®PN-110; 11.9% of the total mass of polyether polyol (DP-2000M from Guodu Chemical); and 0.1% of the total mass of antioxidant (RIANOX®1010 from Tianjin Lianlong New Materials Co., Ltd.) to the reactor. Dehydrate under vacuum at 120°C to -0.95 MPa for 2 hours.

[0062] (2) After cooling to 100℃, add diphenylmethylene diisocyanate (4,4'-MDI) (NCO content 33.6%), which is 19% of the total mass; heat to 115±5℃.

[0063] (3) After reacting for 4 hours, a reasonable NCO value is obtained, that is, the percentage content of NCO is 1.2%, and hot melt adhesive with a solid content of 100% is obtained.

[0064] Comparative Example 2 The polyester polyol, purchased from the market, is brand and model BY3022 from Beijing Boyuan Chemical Co., Ltd. It is a dimer acid polyester polyol without the introduction of epoxy groups or phosphorylation.

[0065] The preparation method of hot melt adhesive is as follows: (1) Based on a total mass of 100 kg of all raw materials for hot melt adhesive, 33% of the total mass of crystalline polyester polyol (Dynacoll 7360) and 54% of the total mass of dimer polyester polyol (BY3022 from Beijing Boyuan Chemical Co., Ltd., which does not have epoxy groups or phosphorylation) were added to the reactor. Antioxidant (RIANOX®1010 from Tianjin Lianlong New Materials Co., Ltd.) was added to the reactor. The reactor was then dehydrated under reduced pressure to -0.95 MPa for 2 hours at 120 °C.

[0066] (2) After cooling to 100℃, add isocyanate, which is 12.8% of the total mass; then heat to 115±5℃.

[0067] (3) After reacting for 4 hours, a reasonable NCO value was obtained, i.e., the NCO percentage content was 1.2%, and the hot melt adhesive was obtained. The solid content of the hot melt adhesive was 100%.

[0068] Performance testing.

[0069] Detection methods.

[0070] 1. The bio-based polyester polyols prepared in each embodiment were subjected to performance tests. The viscosity was measured at 50°C using Brookfield Thermosel (27mm mandrel, 100rpm), the glass transition temperature Tg was measured using DSC, the acid value and hydroxyl value were determined by titration, and the number-average molecular weight Mn was determined by GPC. The performance test results are detailed in Table 1.

[0071] Table 1 Example Viscosity [mPa·s] Tg[℃] Acid value [mg KOH / g] Hydroxyl value [mg KOH / g] Mn Example 1 6300 -10 2.4 45 2493 Example 2 5700 -20 2.3 41 2734 Example 3 8500 3 2.2 48 2337 Example 4 15000 10 2.7 38 2952 Example 5 7600 -5 2.8 42 2671 2. Performance tests were conducted on the hot melt adhesives prepared in each embodiment and comparative example. Initial strength was the strength after 1 minute of curing, tested according to IPC TM-650 4.3.8; T-peel strength was the strength after 24 hours of curing at 25°C, tested according to ISO 8510-1 90° T-peel test; shear strength was the strength after 24 hours of curing at 25°C, tested according to ASTM D1002. The substrates for initial strength and peel strength tests were PVC and aluminum, while the substrates for shear strength tests were steel plate and wood. The test results are detailed in Table 2.

[0072] The shear strength of the hot melt adhesive on different substrates after curing at 25°C for 24 hours was tested according to ASTM D1002. The test results are detailed in Table 3.

[0073] Table 2 Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 initial strength 5N 5.6N 7N 14N 10N 5N 3.5N T-peel strength 55N 60N 65N 78N 68N 50N 45N Shear strength (steel plate) 13MPa 14MPa 15.4MPa 17.2MPa 14.5MPa 12MPa 8Mpa Shear strength (wood) 13.8MPa 14.5MPa 16.4MPa 18.2MPa 14.5MPa 13MPa 11.6 MPa Table 3 Substrate Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 ABS 5MPa 5.6 NMPa 7MPa 14MPa 10MPa 5MPa 2.5Mpa PA 8MPa 8.2MPa 9MPa 15MPa 10MPa 6.6MPa 1.5N PC 7.6MPa 8MPa 9.4MPa 12MPa 10.8MPa 7.5MPa 5.8 MPa PP 0.47MPa 0.43MPa 0.8MPa 2MPa 1.03MPa 0.2MPa 0.13 MPa Through a unique bio-based bicyclic molecular structure and an epoxy-phosphoric acid synergistic mechanism, a bio-based polyester polyol was prepared. Based on this, hot melt adhesives achieved a triple breakthrough in environmental friendliness, ultra-high strength, and universal substrate compatibility, completely breaking through the technical barriers of petroleum-based adhesives. The bio-based content of this application is >70% (the bio-based content testing standard is ASTM D6866), which comprehensively surpasses the 40-50% bio-based content of Henkel's mainstream Technomelt Supra series products for woodworking and furniture. In particular, it solves the industry problem of bonding metals and polar plastics, and its strength is far superior to the hot melt adhesive made from petroleum-based STEPANPOL® PN-110 in Comparative Example 1.

[0074] Compared to Comparative Example 2, which is also a dimerized polyester polyol but does not introduce epoxy groups and phosphorylation, the hot melt adhesives prepared from the polyester polyols in the various embodiments of this application have significantly better performance than the hot melt adhesives prepared from Comparative Example 2.

[0075] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A bio-based polyester polyol for hot melt adhesives, characterized in that: This bio-based polyester polyol is a dimeric acid polyester polyol containing epoxy phosphate groups.

2. The method for preparing the bio-based polyester polyol for hot melt adhesive according to claim 1, characterized in that, Includes the following steps: (1) Flaxseed oil is put into a reaction vessel, and NaOH aqueous solution and water are added under N2 protection to hydrolyze it. Then H2SO4 aqueous solution is added for acidification. After centrifugation, washing and distillation are performed to obtain unsaturated fatty acids. (2) Under N2 protection, antioxidants and unsaturated fatty acids were added to the reactor, the temperature was raised, lipase was added, and a chain terminator was added after the reaction to obtain unsaturated dimers; (3) Under N2 protection, the unsaturated dimer was vacuum dehydrated and dried, cooled to 50°C, antioxidant and chelating agent were added, stirred evenly, hydrogen peroxide was added dropwise for oxidation, and after the reaction, the aqueous phase was washed until it was neutral, the organic layer was separated, and vacuum dehydrated to obtain epoxidized dimer acid. (4) Under N2 protection, add epoxidized dimer acid to the reactor, heat up, add diluted phosphoric acid catalyst dropwise, after reaction, cool down to below 0-5℃, add pyridine catalyst, continue reaction, wash until the aqueous phase is neutral, separate the organic phase, dehydrate under vacuum to obtain bio-based epoxidized phosphorylated dimer acid monomer. (5) Add a mixture of bio-based epoxy phosphorylated dimer monomers and one or more of isosorbide, bio-based diacid and bio-based diol to the reactor in proportion, purge with nitrogen to replace air, and carry out esterification reaction by heating until the acid value drops to 15-22 mgKOH / g. Gradually evacuate the system to reduce the pressure to ≤-0.1 kPa, remove residual water and small molecule byproducts until the acid value is ≤2 mgKOH / g and the hydroxyl value reaches the target value. After the reaction is completed, cool to room temperature, filter to remove impurities, and obtain dimer polyester polyol containing epoxy phosphoric acid groups.

3. The method for preparing bio-based polyester polyol for hot melt adhesive according to claim 2, characterized in that: The hydrogen peroxide has an epoxy rate of 70% to 80% and an epoxy value of 0.25 mol / 100g to 0.28 mol / 100g.

4. The method for preparing bio-based polyester polyol for hot melt adhesive according to claim 2, characterized in that: In step (3), the molar ratio of hydrogen peroxide to the double bond of the unsaturated dimer is 1.2:1 to 1.3:

1.

5. The method for preparing bio-based polyester polyol for hot melt adhesives according to claim 1, characterized in that: In step (4), the reaction rate of the epoxide groups of the phosphoric acid with the epoxide dimer acid is 15%.

6. The method for preparing bio-based polyester polyol for hot melt adhesive according to claim 1, characterized in that: In step (5), the weight of the bio-based epoxy phosphorylated dimer monomer is 31.2% to 81% of the total weight of all raw materials; the weight of the isosorbide is 12.2% to 29.8% of the total weight of all raw materials; the weight of the bio-based diacid is 0% to 28.7% of the total weight of all raw materials; and the weight of the bio-based diol is 0% to 10.3% of the total weight of all raw materials.

7. The application of the bio-based polyester polyol for hot melt adhesives according to any one of claims 1 to 6, characterized in that: The bio-based polyester polyol can be used to prepare hot melt adhesives, which contain isocyanate compounds and at least one bio-based polyester polyol.

8. The application of the bio-based polyester polyol for hot melt adhesives according to claim 7, characterized in that: The hot melt adhesive contains 35% to 65% by weight of bio-based polyester polyols.

9. The application of the bio-based polyester polyol for hot melt adhesives according to claim 7, characterized in that: The coating temperature of the hot melt adhesive is 110–150°C.

10. The application of the bio-based polyester polyol for hot melt adhesives according to claim 7, characterized in that: The hot melt adhesive has a viscosity of 1,000 to 100,000 mPa·s as measured at 120°C.